FIG. 1 shows a schematic diagram of a typical fire alarming system. As shown in FIG. 1, in a fire alarming system, a control panel 160 is connected to a plurality of notification appliances 190 distributed in a building. These notification appliances may be connected to one line network in parallel, and the network is connected to the control panel 160. The notification appliances may obtain electric energy from the fire alarming control panel 160 via the line network and communicate with the fire alarming control panel 160. The notification appliance 190 in FIG. 1, for example, may be a sound alarm and may also be a strobe alarming device, or referred to as a “strobe notification appliance”, while the latter one, for example, uses a xenon lamp or a light-emitting diode (LED), etc. as a light-emitting element.
In recent years, more and more manufacturers use the LED as a light-emitting element of a strobe notification appliance. When there is fire or an emergency, the strobe notification appliance drives the LED to emit strobe light so as to alert people to evacuate in time. Using a high-power LED as the light-emitting element may reduce the electric energy consumption of the strobe notification appliance and simplify the complexity of a drive circuit, and thus it gradually forms a development trend in the field of fire fighting.
FIG. 2 exemplarily shows a typical circuit of a strobe notification appliance. As shown in FIG. 2, a strobe notification appliance 200 comprises a boost circuit 210, an energy storage circuit 220, a drive circuit 230, an LED circuit 240 constituted by a plurality of LED elements connected in series, and a control circuit 250. The boost circuit 210 is connected to an electric energy input end of the strobe notification appliance 200, that is, connected to the line network in FIG. 1. The energy storage circuit 220 may be a large capacitor C1, which is charged by the boost circuit 210. The drive circuit 230 is powered by the energy storage circuit 220, so as to supply a drive current I_work for the plurality of LED elements connected together in series. The LED elements are illuminated under the effect of the drive current. The control circuit 250 controls the frequency and intensity of LED element flashing by sending a control signal Ctrl to the drive circuit 230. The control circuit 250 may be a micro-controller (MCU), and may also be a circuit composed of discrete elements.